OGLE-2016-BLG-0156: Microlensing Event with Pronounced Microlens-parallax Effects Yielding a Precise Lens Mass Measurement (original) (raw)
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Astrophysical Journal, 2001
We present the photometry and theoretical models for a Galactic bulge microlensing event OGLE-2000-BUL-43. The event is very bright with I = 13.54 mag, and has a very long time scale, t E = 156 days. The long time scale and its light curve deviation from the standard shape strongly suggest that it may be affected by the parallax effect. We show that OGLE-2000-BUL-43 is the first discovered microlensing event, in which the parallax distortion is observed over a period of 2 years. Difference Image Analysis (DIA) using the PSF matching algorithm of Alard & Lupton enabled photometry accurate to 0.5%. All photometry obtained with DIA is available electronically. Our analysis indicates that the viewing condition from a location near Jupiter will be optimal and can lead to magnifications ∼ 50 around January 31, 2001. These features offer a great promise for resolving the source (a K giant) and breaking the degeneracy between the lens parameters including the mass of the lens, if the event is observed with the imaging camera on the Cassini space probe. Subject headings: gravitational microlensing -stars: individual OGLE-2000-BUL-43 * Based on observations obtained with the 1.3 m Warsaw Telescope at the Las Campanas Observatory of the Carnegie Institution of Washington.
KMT-2019-BLG-1715: Planetary Microlensing Event with Three Lens Masses and Two Source Stars
The Astronomical Journal, 2021
We investigate the gravitational microlensing event KMT-2019-BLG-1715, the light curve of which shows two short-term anomalies from a caustic-crossing binary-lensing light curve: one with a large deviation and the other with a small deviation. We identify five pairs of solutions, in which the anomalies are explained by adding an extra lens or source component in addition to the base binary-lens model. We resolve the degeneracies by applying a method in which the measured flux ratio between the first and second source stars is compared with the flux ratio deduced from the ratio of the source radii. Applying this method leaves a single pair of viable solutions, in both of which the major anomaly is generated by a planetary-mass third body of the lens, and the minor anomaly is generated by a faint second source. A Bayesian analysis indicates that the lens comprises three masses: a planet-mass object with ∼2.6 M J and binary stars of K and M dwarfs lying in the galactic disk. We point o...
The Astrophysical Journal, 2011
We present the analysis result of a gravitational binary-lensing event OGLE-2005-BLG-018. The light curve of the event is characterized by 2 adjacent strong features and a single weak feature separated from the strong features. The light curve exhibits noticeable deviations from the best-fit model based on standard binary parameters. To explain the deviation, we test models including various higher-order effects of the motions of the observer, source, and lens. From this, we find that it is necessary to account for the orbital motion of the lens in describing the light curve. From modeling of the light curve considering the parallax effect and Keplerian orbital motion, we are able to measure not only the physical parameters but also a complete orbital solution of the lens system. It is found that the event was produced by a binary lens located in the Galactic bulge with a distance 6.7 ± 0.3 kpc from the Earth. The individual lens components with masses 0.9±0.3 M ⊙ and 0.5±0.1 M ⊙ are separated with a semi-major axis of a = 2.5 ± 1.0 AU and orbiting each other with a period P = 3.1 ± 1.3 yr. The event demonstrates that it is possible to extract detailed information about binary lens systems from well-resolved lensing light curves.
Gravitational Binary-Lens Events with Prominent Effects of Lens Orbital Motion
The Astrophysical Journal, 2013
Gravitational microlensing events produced by lenses composed of binary masses are important because they provide a major channel to determine physical parameters of lenses. In this work, we analyze the light curves of two binary-lens events OGLE-2006-BLG-277 and OGLE-2012-BLG-0031 for which the light curves exhibit strong deviations from standard models. From modeling considering various second-order effects, we find that the deviations are mostly explained by the effect of the lens orbital motion. We also find that lens parallax effects can mimic orbital effects to some extent. This implies that modeling light curves of binarylens events not considering orbital effects can result in lens parallaxes that are substantially different from
First Observation of Parallax in a Gravitational Microlensing Event
The Astrophysical Journal, 1995
We present the rst detection of parallax e ects in a gravitational microlensing event. Parallax in a gravitational microlensing event observed only from the Earth appears as a distortion of the (otherwise symmetrical) lightcurve due to the motion of the Earth around the Sun. This distortion can be detected if the event duration is not much less than a year and if the projected velocity of the lens is not much larger than the orbital velocity of the Earth about the Sun. The event presented here has a duration (or Einstein diameter crossing time) oft = 220 days and clearly shows the distortion due to the Earth's motion. We nd that the projected velocity of the lens isṽ = 75 5 km=s at an angle of 28 4 from the direction of increasing galactic longitude, as expected for a lens in the galactic disk.
BINARY MICROLENSING EVENT OGLE-2009-BLG-020 GIVES VERIFIABLE MASS, DISTANCE, AND ORBIT PREDICTIONS
The Astrophysical Journal, 2011
Binary microlensing event OGLE-2009-BLG-020 gives a verifiable mass, distance and orbit predictions. ABSTRACT We present the first example of binary microlensing for which the parameter measurements can be verified (or contradicted) by future Doppler observations. This test is made possible by a confluence of two relatively unusual circumstances. First, the binary lens is bright enough (I = 15.6) to permit Doppler measurements. Second, we measure not only the usual 7 binary-lens parameters, but also the "microlens parallax" (which yields the binary mass) and two components of the instantaneous orbital velocity. Thus we measure, effectively, 6 'Kepler+1' parameters (two instantaneous positions, two instantaneous velocities, the binary total mass, and the mass ratio). Since Doppler observations of the brighter binary component determine 5 Kepler parameters (period, velocity amplitude, eccentricity, phase, and position of periapsis), while the same spectroscopy yields the mass of the primary, the combined Doppler + microlensing observations would be overconstrained by 6 + (5 + 1) − (7 + 1) = 4 degrees of freedom. This makes possible an extremely strong test of the microlensing solution.
Analysis of microlensing events with latest generation telescopes
2020
Gravitational microlensing is an astronomical phenomenon where the gravity of a foreground massive object bends the rays of light of a background source into images. Effectively, the background source appears to be magnified with respect to time. Since this does not require detection of light from the lens, gravitational microlensing can be used to study different populations of objects in the galaxy, even the extra-solar planets. This phenomenon was practically formulated and investigated since the last decade of 20th century by a few observing groups. Today gravitational microlensing is observed and monitored by fourth generation telescopes towards high density stellar fields like the Galactic Bulge, Large and Small Magellanic clouds. With the increased capabilities there are numerous microlensing events that are detected but not yet analysed. Analysing these events, especially formed by a binary lens is not only challenging but tedious task. However with a suitable model that exp...
The Astrophysical Journal, 2016
Light curves of microlensing events involving stellar binaries and planetary systems can provide information about the orbital elements of the system due to orbital modulations of the caustic structure. Accurately measuring the orbit in either the stellar or planetary case requires detailed modeling of subtle deviations in the light curve. At the same time, the natural, Cartesian parameterization of a microlensing binary is partially degenerate with the microlens parallax. Hence, it is desirable to perform independent tests of the predictions of microlens orbit models using radial velocity time series of the lens binary system. To this end, we present 3.5 years of RV monitoring of the binary lens system OGLE-2009-BLG-020L, for which Skowron et al. (2011) constrained all internal parameters of the 200-700 day orbit. Our RV measurements reveal an orbit that is consistent with the predictions of the microlens light curve analysis, thereby providing the first confirmation of orbital elements inferred from microlensing events.